1. Technical Field
The present invention relates to an optical filter and to an optical module that is provided with the optical filter.
2. Related Art
Conventional air-gap-type electrostatically actuated optical filters are known as optical filters for selectively emitting a desired wavelength of light from incident light. In such filters, a pair of substrates are arranged facing each other, a mirror is provided to each of the opposing surfaces of the substrates, electrodes are provided on the periphery of the mirrors, a diaphragm portion is provided on the periphery of one mirror, and the diaphragm portion is displaced by electrostatic force between the electrodes to vary the gap (air gap) between the mirrors, whereby the desired wavelength of light is extracted (see Japanese Laid-Open Patent Publication No. 2003-57438 and Japanese Laid-Open Patent Publication No. 2008-116669, for example).
In such an optical filter, the gap between the pair of mirrors must be controlled in an extremely narrow range of less than one micron to several microns during manufacturing, and it is important that the gap between the mirrors be precisely maintained and controlled to the desired size.
In such an optical filter, the wavelength of light that corresponds to the gap between the mirrors can be selectively extracted by varying the gap between the mirrors.